This invention relates in general to a printer and methods of manufacturing a printer and more particularly to a print engine chassis fabricated using interlocking rigid members that fit together without fasteners and which are coated to hold the rigid members in place.
Pre-press color proofing is a procedure used by the printing industry to create representative images of printed material. This procedure avoids the high cost and time required to produce printing plates and set-up a high-speed, high-volume printing press to produce a single intended image for proofing prior to a production run of the intended image. In the absence of pre-press proofing, a production run may require several corrections to the intended image to satisfy customer requirements, and each of the intended images would require a new set of printing plates. By utilizing pre-press color proofing, time and money are saved.
A laser thermal printer having half-tone color proofing capabilities is disclosed in commonly assigned U.S. Pat. No. 5,268,708 titled xe2x80x9cLaser Thermal Printer With An Automatic Material Supply,xe2x80x9d issued Dec. 7, 1993 in the name of R. Jack Harshbarger, et al. The Harshbarger, et al. device is capable of forming an image on a sheet of thermal print media by transferring dye from a roll of dye donor material to the thermal print media. This is achieved by applying thermal energy to the dye donor material to form an image on the thermal print media. This apparatus comprises a material supply assembly; a lathe bed scanning subsystem, which includes a lathe bed scanning frame, a translation drive, a translation stage member, a laser printhead; a rotatable vacuum imaging drum; and exit transports for the thermal print media and dye donor material.
The Harshbarger, et al. apparatus meters a length of the thermal print media in roll form from a material supply assembly. The thermal print media is measured and cut into sheets of the required length, transported to the vacuum imaging drum, and wrapped around and secured to the vacuum imaging drum. A length of dye donor roll material is metered out of the material supply assembly, measured, and cut into sheets of the required length. The cut sheet of dye donor roll material is transported to and wrapped around the vacuum imaging drum, and superposed in registration with the thermal print media. The scanning subsystem traverses the printhead axially along the rotating vacuum imaging drum to produce the image on the thermal print media. The image is written in a single swath, traced out in a pattern of a continuous spiral, concentric with the imaging drum, as the printhead is moved parallel to the drum axis.
Although the printer disclosed in the Harshbarger, et al. patent performs well, there is a long-felt need to reduce manufacturing costs for this type of printer and for similar types of imaging apparatus. With respect to the lathe bed scanning frame disclosed in the Harshbarger, et al. patent, the machined casting used as the frame represents significant cost relative to the overall cost of the printer. Cost factors include the design and fabrication of the molds, the casting operation, and subsequent machining needed to achieve the precision necessary for a lathe bed scanning engine.
Castings present inherent problems in modeling, making it difficult to use design tools such as finite element analysis to predict the suitability of a design. Moreover, due to shrinkage, porosity, and other manufacturing anomalies, it is difficult to obtain uniform results when casting multiple frames. In the assembly operation, each frame casting must be individually assessed for its suitability to manufacturing standards and must be individually machined. Further, castings also exhibit frequency response behavior, such as to resonant frequencies, which are difficult to analyze or predict. For this reason, the task of identifying and reducing vibration can require considerable work and experimentation. Additionally, the overall amount of time required between completion of a design and delivery of a prototype casting can be several weeks or months.
Alternative methods used for frame fabrication have been tried, with some success. For example, welded frame structures have been used. However, these welded structures require skilled welding and significant expense in manufacture.
Depending on the weight and forces exerted by supported components, a sheet metal structure, by itself, may provide sufficient support for a print engine chassis structure. However, the construction of a sheet metal chassis can require a considerable number of fasteners for assembly. This adds cost and complexity to the chassis assembly operation, adding to the total number of parts needed to build a chassis and increasing the number of manufacturing steps.
Plastic coatings are widely used to protect metal surfaces against rust and corrosion, to provide gripping areas, to insulate, to dampen vibration, and for other purposes. While it is known that a coating can provide additional adhesion between joined sheet metal parts, this principle has not been applied to sheet metal chassis for printers or other imaging devices.
Snap-together assemblies that do not require fasteners have been utilized for electronic devices, as disclosed in U.S. Pat. No. 5,369,549, Kopp, et al., which discloses a casing assembled without tools. However, print engine chassis have been designed to use fastener hardware, which adds cost and complexity to the manufactured printer.
There has been a long-felt need to reduce the cost and complexity of printer fabrication. However, prior art solutions have been limited to the use of conventional castings or weldments, or have employed fasteners for holding chassis parts together.
It is the object of the present invention is to provide a sheet metal frame for a print engine chassis that can be assembled without fasteners. The goal is to provide a chassis that is structurally rigid, has superior vibration dampening, is economical to manufacture, and which can be easily manufactured.
According to one aspect of the present invention, a print engine chassis for supporting an imaging drum and a printhead translation assembly comprises a sheet metal frame. A plurality of interlocking rigid members comprises the sheet metal frame, and a plastic coating bonds the rigid members in place.
According to an embodiment of the present invention, sheet metal pieces are cut to form the interlocking rigid members, having tabs and slots that allow the interlocking rigid members to be quickly assembled by hand in order to form the sheet metal of the chassis. The assembled structure is then coated, by dipping, spraying, or other means, to provide a rigid chassis. The plastic coating provides a seal that adheres to interlocking rigid members and holds them together at slot-and-tab junctions.
A feature of the present invention is the provision of a method for providing a chassis that can be easily manufactured, but is at the same time sufficiently structurally rigid to act as a suitable replacement for a metal casting or weldment in some applications.
An advantage of the present invention is that individual interlocking rigid members can be modified in order to change the design of the chassis, or to modify the size or configuration of the overall structure. This contrasts with methods using a casting, which cannot be easily modified or scaled dimensionally.
Another advantage of the present invention is that individual interlocking rigid members can be fabricated for use with a number of different configurations. By providing alternate slot and tab features on a rigid member, a designer has flexibility which results in potential cost savings by cutting down the number of parts that would be needed to support multiple printer configurations.
Yet another advantage of the present invention is provided by the inherent vibration damping properties of many types of plastic coatings. This vibration damping helps to isolate the print engine chassis from vibration effects caused by motors, fans, vacuum equipment, power supplies, or other components housed within a printer frame.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described illustrative embodiments of the invention.
The invention and its objects and advantages will become more apparent in the detailed description of the preferred embodiment presented below.